Ethylene-vinyl acetate copolymer paper coating composition



United States Patent 3 337,482 ETHYLENE-VINYL ACETATE COPOLYMER PAPERCOATING COMPOSITION Hiroshi Watanabe and Seiichi Takahashi, Kamakura,

Kanagawa' Prefecture, and Akira Shingyochi and Naotaka Watanabe,Yokohama, Kanagawa Prefecture, Japan, assignors to Toyo KoatsuIndustries, Incorporated, Tokyo, Japan, a corporation of Japan NoDrawing. Filed Sept. 20, 1965, Ser. No. 488,785 Claims priority,application Japan, Sept. 24, 1964, 39/ 53,983 17 Claims. (Cl. 260-8)This invention relates to a paper coating composition prepared by mixinga pigment and assistant with a binder comprising a copolymeric emulsioncomprised mostly of polymerized ethylene and vinyl acetate.

An object of the present invention is to provide a paper coatingcomposition to give paper such excellent properties for printingadaptability as gloss, whiteness, light resistance, wet rubbing strengthand picking and a proper stiffness as a coating material for producingsuch fine printing paper as art paper.

It has already been proposed to coat the surface of sized or n-onsizedpaper, such as sulfite pulp paper, with a coating composition consistingof the three elements of a pigment, binder and assistant in order thatthe pigment may be secured to the surface of the paper to be coated, thesurface of the paper may be made smoother and other properties, such asgloss, whiteness and printability, may be improved in printing paper,such as art paper. It is therefore evident that the quality of printingpaper depends on the properties of the coating composition.

Generally the pigment in the paper coating composition is used toincrease the smoothness, whiteness and ink receptivity. As a typicalpigment there is generally used clay, calcium carbonate, titaniumdioxide, barium sulfate, zinc oxide or titanium white. As the binderthere is used casein, starch, soybean protein, synthetic rubber latex'or polyvinyl alcohol so that the pigment may be secured to the materialpaper to be coated and the printability may be elevated. Such binder isgenerally used singly or as mixtures. Further, the quality of the papercoating composition depends to a great extent on the characteristics ofthe binder.

As the assistant there is used a dispersing agent, an antifoaming agent,and/or a leveling agent. The dispersing agent is intended to peptize thepigment, help the dispersion of the constituent substances in the papercoating composition and deposit them uniformly on the material paper tobe coated. As the dispersing agent there is generally used such complexphosphate compounds as sodium metaphosphate, sodium pyrophosphate orsodium tripolyphosphate. The antifoam agent is intended to preventfoaming in coating. Typical antifoam agents include octyl alcohol,silicone oil or pine oil. The leveling agent is intended to maintain thesmoothness of the surface of the paper when coated. Any surface activeagent can be used as a leveling agent.

Conventional fine printing paper is made by coating paper with a coatingcomposition prepared from the abovementioned three main constituents.The properties of the printing paper depend largely on the kind of thebinder in the paper coating composition. As already described, suchnatural binders as casein or starch have been mostly used singly or asmixtures. However, recently synthetic rubber latices, such asstyrene-butadiene copolymer latex or methylmethacrylate-butadienecopolymer latex, have come to be used together with the natural binder,such as those mentioned above, because it had been found that suchsynthetic rubber latices improve the softness and gloss of the coatedpaper, increase its wet rubbing strength, prevent the generation ofpicking and improve high speed printing. As a typical example of suchbinder, there are the casein-synthetic rubber latex or starch-syntheticrubber latex mixtures.

However, paper coating compositions containing a binder comprising asynthetic rubber latex and a natural binder have many defects asdescribed below:

(1) In preparing such paper coating compositions, unless the ioniccharge, if any, present in the pigment and the hydrogen ionconcentration in the binder are at a fixed balance point, the tendencyof the viscosity of the composition to increase will be little.Therefore, in order to reach this fixed balance point, the hydrogen ionconcentration must be strictly adjusted with alkali, such as ammonia.Furthermore, the degree of viscosity increase is different depending onthe origin of the clay or other pigment used. Under such circumstances,it is very difiicult to control viscosity and prepare a suitable papercoating composition.

(2) Even if the hydrogen ion concentration is properly adjusted to givethe desired viscosity, the paper coating composition will tend tofurther increase in viscosity with the lapse of time. Therefore, whencoating paper with said composition by means of a coating machine, themovement of said composition to the material paper from the coatingmachine is not smooth. Consequently, it is very difficult to uniformlycoat the paper with said composition especially when using a bindercomprising a mixture of such synthetic rubber latex as mentioned abovewith starch.

(3) The coated paper obtained by using a binder prepared from bothstarch and a synthetic rubber latex is not adapted to high speedprinting because of the generation of picking. Furthermore, its wetrubbing strength is so low as to be substantially zero. Therefore, it isnot adapted to offset printing and it is difficult to make high qualitypaper to be used for such printing.

(4) When the coated paper obtained by using a binder containing asynthetic rubber latex is exposed to the sun or fluorescent lamps, dueto the unsaturated bond present in the synthetic rubber latex, thebinder will be denatured with the lapse of time, the surface of thecoated paper will become yellow, its gloss will reduce and its stiffnesswill vary and reduce. Therefore, special care must be taken inpreserving the coated paper after printing and this is a great cause inreducing the commodity value of such coated paper.

The present invention provides paper coating compositions in which theabove-mentioned defects are greatly reduced or eliminated and, inaccomplishing these im- 3 provements, uses as binder an emulsion of anethylenevinyl acetate copolymer, i.e., a copolymer of ethylene and vinylacetate or a copolymer of ethylene, vinyl acetate and an ethylenicallyunsaturated mon-oor dicarboxylic acid. The compositions of thisinvention have the following advantages which have not been achievedheretofore:

(1) In preparing the paper coating compositions of the presentinvention, it is not necessary at all to adjust the hydrogen ionconcentration, because the viscosity of any conventionally used pigment,including clay of any origin, specifically will not increase and theviscosity of the prepared composition will not substantially increase.Therefore, in coating the paper with said compositions, it is easy toadjust and control the viscosity.

(2) The viscosity of the compositions will not increase with the passageof time, the paper coated with the compositions will have no substantialpractical disadvantage by the generation of picking and the wet rubbingstrength of the coated paper will be much higher than in the case ofusing such conventional binder as casein, soybean protein, syntheticrubber latex, polyvinyl alcohol together with starch, or mixturesthereof.

(3) The stiffness of the coated paper can be readily varied by varyingwithin the range hereinafter set forth the content of the ethylene inthe ethylene-vinyl acetate copolymer used. Therefore, the fact that thestiffness of the coated paper can be controlled and maintained at anydesired value is a very important advantage to the commodity value ofpaper coated with our compositions.

(4) The fluid characteristics of the compositions of the presentinvention can be properly varied by varying the content of theethylenically unsaturated monoor dicarboxylic acid employed in thecopolymer used as binder. Therefore, a composition having fluidcharacteristics especially adapted to the surface of the particularpaper to be coated can be provided. As a result, high quality papercoated uniformly with the composition are obtained.

(5) The resulting coated paper is extremely high in whiteness. When itis exposed to the sun fluorescent lamps for -a long time, the surface ofthe coated paper will not discolor nor will it lose any gloss at all norwill its stiffness vary at all.

(6) Paper coated with the compositions of the present invention is soimproved in picking value that it can be used on high speed rotaryprinting presses.

The present invention provides a paper coating composition in which thebinder is composed mostly of an emulsion of a copolymer made from O to5% by weight of an ethylenically unsaturated monoor dicarboxylic acid, 2to 30% by weight ethylene and 98 to 70% by weight vinyl acetate. Thenovel compositions contain such pigments as are contained inconventional paper coating compositions and suitable assistantsdispersed therein.

The amount of polymerized ethylene in the ethylenevinyl acetatecopolymer is defined because, when the polymerized ethylene content isless than 2% by weight, the stiffness of the coated paper quicklydecreases, the pigment is likely to peel off the coated paper,especially if the paper is thick, and the coated paper is no longeradapted for high quality use. Furthermore, as the polymerized ethylenecontent becomes 30% by weight, the stiffness of the coated paperincreases but the adhesiveness of the binder decreases and, as a result,the coated paper tends to generate a little picking which, however, isnot enough to present a substantial practical problem. When the 30%limit is exceeded, the generation of picking becomes so great thatpeeled parts are produced in the printed drawn line and not only is thecommodity value of the paper lost but also the peeled parts stain andcontaminate the printing surface and blanket, mix into the ink, andotherwise indirectly deteriorate the printed 4 result and the efficiencyof the printing operation is reduced. Therefore, paper coated with thepaper coating composition in which an emulsion of an ethylene-vinylacetate copolymer containing more than 30% by weight of polymerizedethylene is used as a binder has no practical value as printing paper.

It is also a gerat advantage of the present invention that the stiffnessto be given to the coated paper can be varied by varying, within theabove-mentioned limits, the polymerized ethylene content in thecopolymer used in the binder. In addition, the use of 5% or less of theethylenically unsaturated monoor dicanboxylic acid in the copolymerserves to regulate the fluid characteristics of the paper coatingcomposition made from the copolymer. That is to say, when theethylenically unsaturated monoor dicarboxylic acid is used, theviscosity of paper coating compositions made therewith will not increaseand the compositions will not coagulate but will be capable of beingvery uniformly applied.

Furthermore, when the unsaturated monoor dicarboxylic acid copolymerizedin the ethylene-vinyl acetate copolymer used in the present invention isup to 5% by weight, the viscous fluidity given to the paper coatingcomposition will be reduced in response to the amount of the unsaturatedmonoor dicarboxylic acid. But, when it is more than 5%, the viscousfluidity will not be substantially changed. Therefore, as a practicalmatter, it is preferable to use in the ethylene-vinyl acetate copolymerof the novel compositions high or low amounts of the ethylenicallyunsaturated monoor dicarboxylic acid for paper having a coarse or smoothsurface, respectively.

The ethylenically unsaturated monoor dicarboxylic acid useful in thepresent invention is represented by the general formula wherein R R andR are all hydrogen, or any one of R R and R is an alkyl or carboxylgroup and the remaining are hydrogen. It is preferred that such acidshave not more than 8 carbon atoms. Typical examples of such acids areacrylic acid, methacrylic acid, maleic acid, citraconic acid, furnaricacid and crotonic acid.

In using the ethylene-vinyl acetate copolymer emulsion in the presentinvention as a binder, it is possible to use it together with such wellknown binders which have been conventionally used as starch, casein orpolyvinyl alco- .hol. The amount of the paper coating composition of thepresent invention to be used to coat paper is substantially the same asthat of any conventional paper coating composition. But the amount ofthe above-described binder used in the present invention is generallysmaller than in any conventional case. The paper coating composition ofthe present invention comprises 3 to 30 parts of binder per parts ofpigment. Further, 0.1 to 5 parts of such assistant as has been alreadydescribed and conventionally used may be added to the composition. Asevident from what has been already described, there are practicaldisadvantages in using conventional binders alone, for example, starch,casein or polyvinyl alcohol. Therefore, it is general practice to alsouse a synthetic rubber latex. Besides the defects of such use as havebeen described, it is usual to use an amount of synthetic rubber latexsolids equal to about /3 to /2 the total solids of the binder. As theamount of the synthetic rubber latex is increased, such defects of thesynthetic rubber latex as have been already described will begin toappear in the coated paper. When about /2 the total amount is exceeded,the advantages and disadvantages cancel each other and, as a result, thesignificance of adding the synthetic rubber latex is lost. Below about/3, little effect of using the synthetic rubber latex can be expected.

tetramethylolrnelamine, pentamethylolmelamine, hexamethylolmelamine,N-methoxymethyl N'-methy1olmelamine, dimethylolethylene urea,monomethylol urea, dimethylol urea, dimethylolethyltriazone,dimethylolhy- The ethylene-vinyl acetate copolymer emulsion of the 5droxyethyltriazone, tetramethylolacetylene diurea, dipresent inventioncan be used alone as a binder or tomethylolpropylene urea,dimethyloldihydroxyethylene gether with other conventional hinders. Whencasein, urea, N-butoxymethyl N-methylol urea and N-methoxystarch orpolyvinyl alcohol is used together with the methyl N-methylol urea.ethylene-vinyl acetate copolymer emulsion, there will be For the pigmenCo a n in the P p coating no such cancellation of the effects as in theuse of the 10 position of the present invention there is used anyconvenabove-mentioned conventional binder. Therefore, there tionallyused pigment singly or mixed. However, the fluid is no need of observingan upper limit on the amount of characteristics of the composition ofthe present inventhe ethylene-vinyl acetate copolymer emulsion used. Thetion will not vary with the kind of pigment as is the dislower limit ofthe ethylene-vinyl acetate copolymer solids advantage when using aconventional rubber latex as a of the emulsion used is M; the solids ofthe total hinder For the assistant Contained in the P p coating so thatthe beneficial effects of such use may be obtained. mp si ion of thepresent invention. there can :be used When using the ethylene-vinylacetate copolymer emulthe above-mentioned conventional assistants. Forthe sion together with another binder, such as a synthetic rublevelingagmt to be added to the Composition of the P bar latex, the amount f theSends f i copolymer ent invention there can be used any conventionallyused emulsion can he /2 the amount of the total solids and such SuTfaCeactive agent Especially anionic Surface active amounts f Said copolymeremulsion will greatly i agents and nonionic surface active agents arepreferable. prove the properties of the resulting coating composition.In Preparing the P p Coating composition, if the ah0Vew known bindersare used, the f bl range f' mentioned surface active agent is dispersedin the pigsolids of the ethylene-vinyl acetate copolymer emulsion mentin advance: there will advantages in that the is to of the total bindersolids used. More than that Preparation Will Simplified and in that highmiscibility may well be used Will be obtained.

The pigment and binder in the paper coating c0mp0si The process forpreparing the paper coating compositions of the present invention areindispensable. However, tion the Present invention is not SubstantiallydifihTent as already described, such conventionally used assistants 0111the PTOCedufes used 1'11 Preparing conventional Paper as dispersingagents, antifoaming agents and leveling coating compositions such asthose already described. agents may be properly added depending on thekind of The most general process shall he explained in the pigment beingemployed. The amount of such assistant following. First of all, 100parts of the pigment are mixed to be used can be less than half theamount required for in a kneader or blender. About 20 parts of anaqueous any conventional composition. solution containing 0.1 to 0.5part of a dispersing agent,

In the present inventlon, 0.5 to 5% by weight of the such as sodiumtripolyphosphate, and 0.1 to 0.05 part of binder solids can be replacedwith an N-methylol groupa leveling agent, such as sodiumalkylbenzenesulfonate, containing compound to further improve the wetrubbing are added to the pigment. The mixture is further kneaded.strength of paper coated therewith. Suitable methylol Then, 3 to 30parts of the mixed binder, depending on group-containing compounds arerepresented by any of the character to be given to the paper to becoated, are the general Formulae I to IV. added to-the mixture. Themixture is then diluted with Y N X- MP 2 air 2|: NH M1 (MzhHN-fil(|JNH(M1),,

M1-N /NM2 O=O\ N /N g El; NHM2 o O 2)n (I) h i water to a concentrationadapted for the coating machine to be used and is further mixed well. jxcalj bg CHOH, Paper is coated with the thus-obtained mixed composi- 9tion at a concentration in a wide range, for example, about 20 to 70%solids in water depending on the coat- H (|J-(|3H ing equipment to heused, for example, a roll coater or a MIN NMz knife coater. In preparingthe paper coating composition of the present invention, it is notnecessary to adjust the (n hydrogen ion concentration. In case casein isused as a pfirrt of the 'binder, in mixing and kneading the binder witht e pigment, if a small amount of ammonia is added to (c) Y 18 CH2Whafeln 15 lower alkyl the binder, the dissolution of the casein will beassisted. (fi l/$ 5322? 3 :5 Any conventional paper can be coated in thepresent (6) eah of M2 a 3 is H or a CH2OR1 g p invention. That 1s tosay, paper to be coated with the wherein R1 is a lower alkyl group and nis 1 or coating composition of the present mvention is paper I I madethrough the general steps of beatmg such single or Typical examples ofthese compounds are monomethn ed r w material pulp as a ground pulp,semichernical ylolmelamine, dimethylolmel-amine, trimethylolmelamine,pulp, sulfite pulp, kraft pulp or brown. ground pulp, sizing the pulp,adding known fillers to the pulp, coloring and refining the resultingmixture and making it into paper. A gloss is given to the surface of thepaper by means of calender rolls or the like. Nothing is deposited onthe surface. Only fibers are exposed on the surface.

The method of applying the paper coating composition of the presentinvention is exactly the same as any suitable conventional method. Theamount of the coating composition of the invention applied per unit areaof the material paper can be the same as in the case of the conventionalpaper coating. Typical coating methods are on-machine coating, sizepress coating, olfmachine coating and board coating methods. There canbe used such well known coaters as a roll coater, brush coater, sizingpress, printing coater, casting coater, air knife coater, championmachine coater, blending coater and combination coater. The papercoating composition of the present invention may be prepared and appliedaccording to the operating specification of the coater for the object ofthe coated paper.

The ethylene-vinyl acetate copolymer emulsion to be used in the presentinvention can be obtained by such known treatment as, for example, inJapanese Patent 420,428. However, the emulsion obtained by the followingtreatment has an especially favorable effect on the attainment of theobjects of the present invention. 1000 parts of vinyl acetate (to whichis added unsaturated ethylenic monoor dicarboxylic acid if used), 45 to90 parts of such nonionic surface active agent as polyoxyethylene oleylphenyl ether or polyoxyethylene lauryl phenyl ether, to parts of laurylalcohol sulfate, 1000 parts of distilled water, 0.5 to 1 part of sodiumhydrogen sulfite as a catalyst (1) and 0.5 to 2 parts of sodiumcarbonate as a hydrogen ion concentration adjusting agent are put into areaction chamber and ethylene is well saturated under a pressure of 10to 80 kg./cm. while they are being well stirred at 40 to 60 C. Then anaqueous solution prepared by dissolving 0.5 to 5 parts of potassiumpersulfate as a catalyst (2) in 200 parts of water is graduallycontinuously added under pressure into the reaction chamber over thefirst four hours of the reaction time. When the above-mentioned aqueoussolution prepared by dissolving 0.5 to 5 parts of potassium persulfateis added into the reaction chamber, a reaction will start. The reactionis carried out under the conditions of a reaction temperature of 40 to60 C. and a reaction pressure (ethylene pressure) of 10 to 80 kg./cm. In10 hours after the reaction starts, an ethylene-vinyl acetate copolymeremulsion of a solids concentration of about 40 to 55% by weight will beobtained. The content of ethylene in the obtained copolymer will berelated to the ethylene pressure used. When the ethylene pressure is 10kg./cm. the content of ethylene in the copolymer will be about 2% byWeight. When the ethylene pressure is 80 kg./cm. the content of ethylenein the copolymer will be about 30% by weight. The content of ethylene inthe copolymer in this range will be linearly proportional to theethylene pressure. Furthermore, when an ethylenically unsaturated monoordicarboxylic acid is used, the amount of vinyl acetate put into thereaction chamber may be correspondingly reduced by the number of mols ofthe unsaturated monoor dicarboxylic acid used. In the emulsion obtainedby such method, the polymeric solids comprise substantially uniformspheres of diameters of 0.1 to 0.3 The emulsion is highly stable onstanding.

The reason why the composition of the present invention is moreeffective than any conventional composition is that, as mentioned above,an ethylene-vinyl acetate copolymer emulsion having a composition ratioin the specific range as set forth is used as a binder. Such papercoating compositions of the present invention are simple to prepare. Inthe case of coating paper with such compositions by means of a coatingmachine, there will be no inconvenience in handling due to viscosity orthe like and therefore the workability of the composition is high.Furthermore, after the paper coating compositions are prepared, there issubstantially no tendency of the viscosity to increase or otherwisechange with the lapse of time and the compositions are stable.Therefore, the paper coated with the compositions of this invention haveno such defects found in the conventional paper coating compositions asdescribed hereinabove and have numerous excellent performancecharacteristics. Thus, the paper coating compositions of the presentinvention are very useful in industry.

The subject matter and working of the present invention shall be madeclearer with the following examples wherein parts and percentages are byweight unless otherwise noted.

Example 1 Each of the several paper coating compositions indicated inTable 1 where prepared as follows. A mixture of 75 parts of kaolin clayproduced in Georgia, U.S.A., 25 parts of fine powdery calcium carbonatehaving a particle size of 0.1 to 5p. and 100 parts of distilled waterwas kneaded by means of a kneader for about 30 minutes. 0.2 part ofsodium tripolyphosphate was then added to the mixture and the mixturewas mixed and kneaded for another 10 minutes. To this mixture were added15 parts, based on solids, of the ethylene-vinyl acetate copolymeremulsion constituted as shown in Table 1 in the cases where thecopolymer was used alone as binder or 7 parts, based on solids, of saidcopolymer emulsion and 8 parts, based on solids, of any known binder asindicated in the cases where the copolymer was used together with suchknown binder. The mixture was mixed and kneaded, while adding water, ifnecessary, to prepare a paper coating composition to form a slurryhaving a solids concentration of 50% by weight.

Commercial high quality unbleached sulfite paper having a weight of 84g./m. and a sized degree of 58 seconds was hand-painted on one surfacewith each of the paper coating compositions prepared above by means ofapplicator bars having a clearance of 1 micron so that the paper wascoated with 20 g. of the solids of each paper coating composition persquare meter of the paper. The paper was dried at the normal temperaturefor 2 hours and then with hot air at C. Then the treated paper waspassed 4 times by nipping through a testing super calender at atemperature of 70 0., roll pressure of kg./cm. water absorption of thetreated paper of 6 to 8% by weight and speed of 25 m./min. The resultsof the measurements of the viscosity of the applied paper coatingcomposition and the whiteness, light resistance, yellow change degree,wet rubbing strength, picking value and stiffness of the treated paperare compiled and shown in run numbers 1 to 27 (of which 21 to 22 are ofcomparisons) in Table 1.

Further, as comparisons, such styrene-butadiene andmethylmethacryl'ate-butadiene copolymer emulsions of generally usedconventional composition ratios as are shown in Table 1 were usedinstead of the ethylene-vinyl acetate copolymer emulsions in the manneras described above, to form paper coating compositions using the sameamounts of exactly the same pigment and assistant as in the case of eachof the above-mentioned run numbers 1 to 27 in substantially the sameprocesses as in each of said run numbers. The same type of paper wascoated using the same coating process as in the case of each of theabove-mentioned run numbers 1 to 27. These results are also compiled andshown in run numbers 28 to 31.

TABLE 1 Solid substances in the binders Paper coating compositions RunNo. Ethylene-Vinyl acetate copolymer composition Viscosity in Viscosityin in percent by weight centipoises at eentipoises Additional bindersused the time of the after the preparation preparation Ethylene Vinylacetate Acrylic acid (note 1) (note 2) 5 95 287 285 94 1 253 265 85 0247 235 15 84 1 231 l 230 5 95 0 629 630 5 95 0 526 532 5 95 0 Soybeanprotein. 458 461 5 95 0 Polyvinyl alcohol. 360 360 5 94 1 Oxidizedstarch..- 611 610 5 94 1 Casein 480 482 5 94 l Soybean protein. 446 4505 94 1 Polyvinyl alcohol- 349 351 15 85 0 Oxidized starch.v 592 602 1585 0 Casein 456 458 15 85 0 Soybean protein. 436 443 15 85 0 Polyvinylalcohol. 332 333 15 84 1 Oxidized starch..- 531 542 15 84 1 Casein 432435 15 84 1 Soybean protein.. 403 400 15 84 1 Polyvinyl alcohol. 310 3130 Casein 421 425 35 64 1 410 411 2 98 0 490 495 2 97 1 423 421 2 3 352354 2 93 5 298 299 2 91 7 289 290 1, 121 2, 351 Butadiene. 40 890 1, 9922 1, 740 2, 990 920 1, 365

Properties of the coated paper Run Light Wet No. whiteness Gloss degreeresistance rubbing Picking Stifiness in percent in percent in percentYellowing degree (note 6) strength value (note 9) Remarks (note 3) (note4) (note 5) (times) (note 8) (note 7) Y 79.6 34.2 98. 2 No change 10 188141 78. 7 35.6 96. 3 d 192 139 86. 5 37. 9 187 127 87. 7 32. 3 188 78. 733. 1 170 129 82.0 32. 8 I 163 133 85.1 29. 3 188 135 84. 3 27. 1 172135 87.3 34. 5 171 136 81.9 29. 8 183 134 Examples of the 79. 0 31. 5173 1336 present invention. 82. 2 31. 5 177 137 79. 8 32. 9 161 121 85.6 31. 0 175 122 87. 6 31. 3 165 126 87. 5 32. 3 165 123 81. 7 30. 9 12484. 6 32.8 190 128 88. 7 34. 0 119 as a a 79. 2 81.2 29.6 129 114 82.332. 7- 141 172 85. 9 31.9 142 178 Examples of the 84. 2 32.8 a 188 172present invention. 83.1 33.1 189 168 83,7 32.4 1 181 172 775. 1 13. 3136 2. 3 1 6 31 75. a 21. 2 139 137 Cmmmm- 73. 9 23. 5 121 135 1 Styrene60. 2 Butadlene 40.

The respective properties of the coated paper in Table 1 were measuredby the following methods:

Notes 1 and 2: Measured at a rotating speed 015-60 rpm. at 20 C. bymeans of a viscosimeter. In note 2, the viscosity was measured 24 hrs.after preparation.

Note 3: Measured with a reflectometer' in accordance with ASTM D985-48T.v

,Note 4: Measured in accordance with ASTM D1223- 52T. 1

Note 5: The sample was irradiated with ultraviolet rays for 24 hourswith a Fade-O-meter' and the ratio of the whiteness after theirradiation to the whiteness before the irradiation is represented inpercent.

8 Methyl-methacrylate 60.

' number of rubbing times until the white pigment peeled off andappeared on the surface of the black paper below it is shown.

Note 8: The coated paper was tested with N0. 4 ink under a printing r011pressure of 30 kg./cm. by means 1 I of a printability testing machineand the distance of the strip off of which the printing. ink peeled isshown in Table l.

. Note 9: Measured with. a. stiifness tester in. accordance casein,starch, oxidized starch, soybean protein, and polyvinyl alcoholcomprises /s to of said binder.

3. A coating composition as claimed in claim 1 wherein 0.5 to 5 weightpercent of said binder is replaced by an with TAPPI Standard T451m-45.The stiffness of the un- 5 N-me-thylol compound from the classrepresented by any coated paper was 102. of the general formulae E am le2 Y NH M x p X.X X/ \XO=G In each of runs 32 through 37, a mixture of 75parts l i l; 1 of kaolin clay produced in Huber, U.S.A. and 25 parts ofi fine powdery calcium carbonate having a particle size of if i 0.1 to51.4 with 100 parts of distilled water was kneaded 0 0 by means of akneader for about 30 minutes. 0.2 part of and calcium tripolyphosphatewas then added to the mixture N and the mixture was mixed and kneadedfor 10 minutes. To this mixture were added 6.5 parts of anethylene-vinyl (AMEN-(3 (|3 NH (M911 acetate copolymer containing 10% byweight ethylene, N 89% by weight vinyl acetate and 1% by weight maleic Kacid and, as shown in Table 2, 0.3 part of a methylol lradical-containing compound and 8 parts of starch or NH M2 H casein asindicated were added. The mixture was mixed whemin and kneaded, whileadding water if necessar to prepare a paper coating composition in theform of it slurry hav- (a) X 18 Selected from CHOH; ing solidsconcentration of 50% by weight. Commercial 2 '(b) X X can be highquality unbleached sulfite paper of a weight of 84 g./m. and a sizeddegree of 5 8 seconds was hand-painted I on one surface with said papercoating composition by M1N means of applicator bars of a clearance of 1micron so 0 that paper is coated with 20 g. of the solid part of the i,above-prepared composition per square meter of the paper. The paper wasdried at the normal temperature for 2 hours (0) Y is selected from CHand RN wherein R is and then with hot air at 80 C. Then the treatedpaper selected from lower alkyl and hydroxy lower alkyl; was passed 4times by nipping through a testing super (d) M is -CH OH; calender at atemperature of 70 C., roll pressure of 100 (e) each of M and M isselected from H and a kg./cm. water absorption of the treated paper of 6to CH OR group wherein R is a lower alkyl group 8% by weight and speedof 25 m./ min. The results of the and n is an integer from 1 to 2.measurements of the viscosity of the applied paper coating 4. A coatingcomposition claimed in claim 1 wherein composition and the whiteness,light resistance, yellow said aqueous mixture comprises 20 to 70%solids. change degree, wet rubbing strength, picking value and 5. Papercoated with the composition claimed in stiffness of the treated paperare compiled and shown in claim 1. Table 2. The measurements wereconducted in the same 6. Composition claimed in claim 1 wherein saidacid manner as those in Table 1. is acrylic acid.

TABLE 2 Solid substances in the binders Paper coattgngS compo-Properties of the coated paper Run Viscosity Viscosity No. Additional ineentiin centi- White- Gloss Light re- Yellow Wet Methylol radicalconbinders poises at poises after ness in degree sistance changederubbing Picking Stiffness taining compound used the time the prepapercent in perin pergree strength value of the prepration cent cent(times) aration 32 Hexamethylolmel- Starch 621 V 623 78.7 31.1 98.2 Nochange. 15 188 131 M t ii iiiimeiamine do 613 607 79.2 33.7 97.9 do 15192 132 Dimethylolethylene do 625 625 31.1 p 32.4 97.6 do 15 173 131 M rrh methyloluremflfl Casein 627 628 81.5 33.9 98.2 ..do 15 179 129Dimethylolpropylene do. 599 603 72.3 33.6 97.1 .do 15 188 133 37"-.- Nbfiiioxy methylN ..do. 608 611 73.9 34.0 a 98.2 .do 15 132 135 methylolurea.

Note: The respective methods of measuring the'viscosity, granularity,whiteness, gloss degree, ligit resistance, yellow change degree, wetrubbing strength, picking value and stifines in the above Table 2 weresubstantially the same as in the notes in What is claimed is:

1.. A. coating composition for paper comprising an 6 is xample 1.

7. Composition claimed in claim 1 wherein said acid maleic acid.

8. Composition claimed in claim 2 wherein said member is starch and saidacid is acrylic acid.

9. Composition claimed in claim 2 wherein said member is casein and saidacid is acrylic acid.

10. Composition claimed in claim 3 wherein said N- methylol compound isan N-methylolmelamine.

11. Composition claimed in claim 3 wherein said N- methylol compound isan N-methylolethylene urea.

12. Composition claimed in claim 3 wherein. said N! methyl-e 1 compoundis an N-methylol urea.

13. Composition claimed in claim 3 wherein said N- methylol compound isan N-methylol propylene urea.

14. Composition claimed in claim 2 wherein said memher is soybeanprotein and said acid is acrylic acid.

15. Composition claimed in claim 2 wherein said memher is polyvinylalcohol and said acid is acrylic acid.

16. Composition claimed in claim 2 wherein said memher is starch andsaid acid is moleic acid.

17. Composition claimed in claim 2 wherein said memher is casein andsaid acid is moleic acid.

References Cited Lamar et =al., Adhasion, 1962, 6, No. 12, 629-36.

WILLIAM H. SHORT, Primary Examiner. E. M. WOODBERRY, Assistant Examiner.

Notice of Adverse Decisions in Interferences In Interference No. 96,627involving Patent No. 3,337,482, H. VVatanabe, S. Takahashi, A.Shingyochi and N. Vatanabe, ETHYLENE-VINYL AO- ETATE COPOLYMER PAPERCOATING COMPOSITION, final jud me rnt adverse to the patentees wasrendered June 9, 1972, as to claims 1, 2, 3, 4 5, and 11.

[Ofiicial Gazette Zllawch 237, 1.973.]

1. A COATING COMPOSITION FOR PAPER COMPRISING AN AQUEOUS MIXTURECONTAINING 100 WEIGHT PARTS PIGMENT AND 3 TO 30 WEIGHT PARTS OF A BINDERCOMPRISING A COPOLYMER OF 2 TO 30 WEIGHT PERCENT ETHYLENE, 98 TO 10WEIGHT PERCENT VINYL ACETATE, AND 0 TO 5 WEIGHT PERCENT OF ANETHYLENICALLY UNSATURATED ACID SELECTED FROM THE CLASS CONSISTING OFACRYLIC, METHACRYLIC, MALEIC, CITRACONIC, FUMARIC AND CROTONIC ACIDS.